The present disclosure relates to a comparator, a solid-state imaging device, an electronic apparatus, and a driving method, and particularly to a comparator, a solid-state imaging device, an electronic apparatus, and a driving method with which low power consumption and a decrease in size can be achieved.
In the related art, in an electronic apparatus that includes an imaging function such as a digital still camera and a digital video camera, for example, a solid-state imaging device such as a complementary metal oxide semiconductor (CMOS) image sensor or a charge coupled device (CCD) is used. The solid-state imaging device includes a pixel in which a photo diode that performs a photoelectric conversion and a plurality of transistors are combined, and an image is built based on pixel signals output from the plurality of pixels disposed in a plane.
For example, in the solid-state imaging device, charges accumulated in the photo diode are transferred to a floating diffusion (FD) unit that has a predetermined capacitance and is provided on the connection unit between the photo diode and a gate electrode of an amplifier transistor. Then, a signal corresponding to a level of the charges kept in the FD unit is read out from the pixel, and is analog digital (AD) converted by an AD conversion circuit which has a comparator, and then, is output.
In the solid-state imaging device, as a signal processing for removing a pixel-specific noise, for example, a correlated double sampling processing is performed with respect to the pixel signal output from the pixel. In the correlated double sampling processing, a signal (P-phase) with a level in which the charges accumulated in the FD unit is reset and a signal (D-phase) with a level in which the charges generated in the photo diode are kept in the FD unit, are sampled. Then, the noise can be removed by obtaining a difference of each sampled value.
In the CMOS image sensor, in a case where simultaneity of a shutter closing is retained, the charges are transferred in full batch from the photo diode to the FD unit, and thereafter, the pixel signal is sequentially read out. In this case, a driving of reading the D-phase (signal level) first and the P-phase (reset level) next (hereafter, appropriately referred to as a D-phase first-read drive) is performed (for example, refer to Japanese Unexamined Patent Application Publication No. 2001-238132).
For example, in Japanese Unexamined Patent Application Publication No. 2011-229120, in a comparator circuit which performs the D-phase first-read drive, a solid-state imaging device having a configuration in which an external initial voltage is applied for setting (adjusting) an internal node such that the comparator can operate in accordance with the D-phase signal level, is disclosed.